1. Field of the Invention
The present invention relates generally to hydraulic torque wrenches.
2. Prior Art
There has been an increasing development of torque wrenches, particularly hydraulic torque wrenches, to meet the ever rising need to service heavy industrial equipment wherein a high controllable torque is needed to loosen the large threaded bolts and nuts used in such equipment.
Examples of the present state of the art can be seen in the following U.S. patents:
______________________________________ INVEN- U.S. PAT. NO. TOR ISSUED TITLE ______________________________________ 3,745,858 Biach 07/17/73 TORQUING DEVICE 3,930,776 Keller 01/06/76 HYDRAULIC WRENCH 4,027,561 Junkers 06/07/77 HYDRAULIC WRENCH 4,060,137 Bickford, 11/29/77 TORQUE WRENCH et al 4,308,767 Wilmeth 01/05/82 STUD WRENCH 2,615,682 Stone 10/28/52 PIPE TONG ______________________________________
and the following foreign patents:
______________________________________ PATENT NUMBER INVENTOR ISSUED ______________________________________ German 2,749,857 Wagner 10/05/79 Great Britain 972,449 Sexton 10/14/64 publication date ______________________________________
These prior art wrenches generally use a relatively complex system of gears, bushings, drive pawls, pins, etc., which require the wrench to be relatively large and heavy in physical size and weight and which further gives rise to equipment failure through more and varied sources.
Additionally, because the clamping power of these fittings does not increase as the torque applied to the nut or bolt increases, rounding of the corners of the nuts and bolts occurs which makes the applicability of the fittings less effective.